1. Field of the Invention
The present invention relates to a sorter with movable bins and particularly to a controlling method for the sorter with movable bins capable of sorting in both directions from the upper step to the lower step and from the lower step to the upper step.
2. Description of the Prior Art
In the past, a sorter of one-way sorting system such as sorting from the upper step to the lower step or sorting from the lower step to the upper step has widely been employed. This will be explained referring to the drawings. FIG. 1 illustrates a sorter 2 with 5 movable bins connected to the paper exit 11 of the copying machine 1. FIG. 1(a) shows a situation where the lowest bin S.sub.1 out of 5 bins is connected to the paper exit 11 and is capable of receiving copy papers. Now, if the copying is made with the number of copies set which is 3 on the copying machine one sheet of copy is delivered from the paper exit 11 of the copying machine 1 and is inserted into the bin S.sub.1, then bins are moved downward by one step, thus the second copy is inserted into the bin S.sub.2 and further downward movement of bins by one step enables the 3rd copy to be inserted into the bin S.sub.3 and it stops. FIG. 1(b) shows this situation.
If further copying is made for the second original without changing the number of copies set, bins of the sorter 2 move upward by two steps on the one-way sorting system and the first copy is inserted into the S.sub.1, the second copy into the bin S.sub.2 and the 3rd copy into the bin S.sub.3 again.
On the sorter with one-way sorting system, after the copy paper is inserted into the bins S.sub.3, next copy is to be inserted into the bin S.sub.1, therefore excessive time for returning travel is required for the movement of bins and thereby the copying operation is interrupted. If the moving speed of bins is raised for the shorter interruption time, there have been drawbacks that the driving motor should be large, power consumption is increased and noises are generated.
A sorter of both directions sorting system is one wherein aforesaid drawbacks have been improved. Following is an explanation on the previous example. FIG. 1(b) shows a situation wherein three copies are completed when the copying is made for the first original with the number of copies set which is 3. Next, if the further copying is made for the second original without changing the number of copies set, bins of the sorter 2 do not move and the first copy is inserted into the bin S.sub.3, the second copy into the bins S.sub.2 with a movement of bins upward by one step and the 3rd copy into the bin S.sub.1 with further movement of bins upward by one step, on the sorter of both directions sorting system. FIG. 1(c) shows this situation. In the both directions sorting system, the time for returning to the original position is not needed in this way, the copy operation will not be interrupted.
Therefore, the sorter with movable bins that can comply with the high speed copying with a relatively low speed of bin movement can be realized with a both directions sorting system. It also has merits that low noise, low power consumption and low cost can be realized because the moving speed of bins is low.
However, there have been drawbacks even on the both directions sorting system. For example, if the copying is made with the number of copies set which is 4 under the condition of FIG. 1(b), the first copy is inserted into the bins S.sub.3, the second copy into the bin S.sub.2 with a movement of bins upward by one step and the 3rd copy into the bin S.sub.1 with a further movement of bins upward by one step. Since the 3rd copy corresponds to the bottom step of the bin, the 4th copy is inserted into the bin S.sub.2 with a downward movement of bins by one step. Thus, two same copies are inserted into the bin S.sub.2 as shown in FIG. 1(d), which causes erroneous operation for paper collation.